This invention relates to the treatment of water. More particularly, this invention relates to a system or method for treating water to produce water having biologically acceptable levels of bacteria.
In the past, there have been many different types of water treatment methods and systems proposed to treat water in order to remove contaminants and kill bacteria. In particular, it is known in the prior art to introduce bacteriacides to kill bacteria in the water. For example, U.S. Pat. No. 4,198,296 to Doumas proposes a method for treatment of water by passing the water through a media of activated carbon impregnated with silver salts and metallic silver to increase the amount of silver ions Ag+ to a level which can kill the bacteria. The silver ions Ag+ remain in the water for a period of time necessary to kill bacteria, in the order of six minutes. The water can then be further treated and/or filtered prior to human consumption.
However, in many cases, bacteria which can grow in water may be found in several locations. For example, bacteria which grow in water may be airborne or may be found on surfaces within the actual water treatment system and re-contaminate the water. Furthermore, there is always the possibility that not all of the bacteria in the water has been killed, such that the remaining bacteria may continue to multiply while the water is being held for later use. Therefore, water which has been subjected to disinfection and treated to kill bacteria, may become recontaminated with the same bacteria which were killed by the disinfection. This is particularly likely in warm environments where bacteria and viruses are known to grow faster and be airborne in greater amounts. This may also occur in environments and/or countries which have poor sanitation and may have more bacteria, both airborne bacteria and non-airborne, throughout the environment.
Furthermore, many prior art devices and methods require a long holding time to permit the bacteriacide to kill the bacteria and viruses. This decreases the efficiency of the overall water treatment system, and, requires large amounts of water to be treated at any one time so as to ensure a sufficient supply of treated water when desired.
In some prior art water treatment systems, ultraviolet light is sometimes used substantially immediately before the water is consumed to kill any bacteria which may have recontaminated the water while it was being held for consumption. However, ultraviolet treatment occasionally does not kill all of the bacteria in the water, depending on the intensity of the ultraviolet light, the characteristics of the water itself (i.e. colour, turbidity, organic content), and, the quantity of bacteria in the water. Furthermore, ultraviolet light tends to be inconsistent and bacteria and viruses may not always be exposed to all of the water as it passes in front of the ultra violet light source.
Accordingly, there is a heed in the art for a system and method to treat water so as to ensure a supply of water having biologically acceptable levels of bacteria by killing bacteria in water, and also preventing recontamination of the water before the water is desired to be consumed. There is also a need in the art to quickly treat water so as to rapidly kill bacteria, thereby ensuring a ready supply of treated water. Quickly treating water to rapidly destroy bacteria also avoids the need for large holding containers which are used to treat large amounts of water to ensure water is available at any particular time, and, increases the efficiency of the overall system.
Accordingly, it is an object of this invention to at least partially overcome the disadvantages of the prior art. Also, it is an object of this invention to provide an improved type of water treatment system and method which ensures a supply of water having a biologically acceptable level of bacteria when the water is desired to be consumed by ensuring the bacteria which are killed do not recontaminate the water supply.
Accordingly, in one of its aspects, this invention resides in a method for treating water for human consumption comprising the steps of: (a) introducing a bacteriacide to the water in an amount sufficient to kill bacteria in the water; (b) maintaining the bacteriacide in said water until the water is desired to be consumed and at least for a period of time sufficient to kill the bacteria in the water; (c) once the water is desired to be consumed, decreasing the amount of the bacteriacide in the water to a biologically acceptable amount for human consumption.
In a further aspect, this invention resides in a system for treating water for human consumption comprising: a container for holding the water until the water is desired for human consumption; means for introducing a bacteriacide to the water in the container in an amount sufficient to kill bacteria in the water; means for decreasing the bacteriacide to a biologically acceptable level when the water is desired to be consumed; wherein the bacteriacide is maintained in the water in the container in an amount sufficient to kill bacteria in the water and to prevent recontamination of the water by bacteria until the water is desired to be consumed.
One advantage of the present invention is that maintaining the bacteriacide in the water for an extended period of time will ensure that all the bacteria and viruses have been killed before consumption. Furthermore, maintaining the bacteriacide in the water until substantially immediately before the water is desired to be consumed, decreases the likelihood that the water will become recontaminated with the same bacteria and viruses. In addition, maintaining the bacteriacide in the water until substantially immediately before the water is desired to be consumed, decreases the ability of any bacteria which may have survived the bacteriacide, to reproduce in substantial quantities.
A further advantage of the present invention is that the same disinfecting treatment which is used to initially kill the bacteria is also used to prevent recontamination of the bacteria. Accordingly, the present invention provides a cost savings over other water treatment systems and methods which require a secondary type of water treatment method, such as ultraviolet radiation, in addition to the primary type of water treatment used to initially kill the bacteria.
A further advantage of the present invention is that the bacteriacide, in a preferred embodiment, is a silver ion Ag+ which can be introduced rapidly by means of a silver containing electrode. This provides rapid dissemination of silver ions throughout the water in order to rapidly kill the bacteria, thus decreasing the time required to treat the water and increasing the overall efficiency of the system.
A further advantage of the present invention is that the silver ions Ag+ may be removed by passing the water through an ion exchange to remove the silver ions Ag+. The ion exchange removes the silver ions Ag+, which have acted as the bacteriacide, and further removes other ions and contaminants in the water in addition to the silver ions Ag+. Furthermore, the silver ions Ag+ removed by the ion exchange can then be extracted and recycled in new electrodes for later use.
Further aspects of the invention will become apparent upon reading the following detailed description and drawings which illustrate the invention and preferred embodiments of the invention.